Photoassociative Spectroscopy as a Self-Sufficient Tool for the Determination of the Cs Triplet Scattering Length

In photoassociation spectroscopy, the line intensities of a given vibrational progression exhibit zero-signal modulation reflecting the node structure of the $s$-wave ground state wave function of two free colliding atoms. This leads to the determination of the scattering length. We performed photoassociation of cold Cs atoms polarized in the Zeeman sublevel $f=4\mathrm{}$, $m_f=4\mathrm{}$. We analyzed the intensities of the lines associated with the ${\mathrm{Cs}}_2$ $0_g^{-}$ state dissociating to the ${6s}_{1/2}{+6p}_{3/2}$ asymptote. This yields a value of the Cs triplet state scattering length, $a_T{=-530a}_0$, while consistency requirements impose a value of the multipole ground state molecular coefficient, $C_6=6510\mathrm{}$ a.u.